Carbon Stable Isotope Fractionation of Sulfamethoxazole during Biodegradation by Microbacterium sp. Strain BR1 and upon Direct Photolysis

Abstract

Carbon isotope fractionation of sulfamethoxazole (SMX) during biodegradation by Microbacterium sp. strain BR1 (ipso-hydroxylation) and upon direct photolysis was investigated. Carbon isotope signatures (δ(13)C) of SMX were measured by LC-IRMS (liquid chromatography coupled to isotope ratio mass spectrometry). A new LC-IRMS method for the SMX metabolite, 3-amino-5-methylisoxazole (3A5MI), was established. Carbon isotope enrichment factors for SMX (ε(C)) were -0.6 ± 0.1‰ for biodegradation and -2.0 ± 0.1‰ and -3.0 ± 0.2‰ for direct photolysis, at pH 7.4 and pH 5, respectively. The corresponding apparent kinetic isotope effects (AKIE) for ipso-hydroxylation were 1.006 ± 0.001; these fall in the same range as AKIE in previously studied hydroxylation reactions. The differences in SMX and 3A5MI fractionation upon biotic and abiotic degradation suggest that compound specific stable isotope analysis (CSIA) is a suitable method to distinguish SMX reaction pathways. In addition, the study revealed that the extent of isotope fractionation during SMX photolytic cleavage is pH-dependent.

Liquid chromatography/isotope ratio mass spectrometry analysis of halogenated benzoates for characterization of the underlying degradation reaction in Thauera chlorobenzoica CB‐1T

“…Since then new applications for CSIA have involved the analysis of non volatile, aqueous soluble compounds from more complex mixtures in the fields of pharmaceuticals, nutrition and food authentication, e.g. amino acids, carbohydrates as well as organic acids …”

“…amino acids, carbohydrates as well as organic acids. [5][6][7][8][9][10] Nevertheless, a limited number of applications for LC/IRMS are available in comparison with those for GC/IRMS, mainly as a result of restrictions in the aqueous mobile phase compositions and flow rates that can be employed. As solely inorganic and therefore pure aqueous mobile phases and low flow rates can be used, chromatographic separation is challenging and column stability is becoming a major issue.…”

Perspectives on the antibiotic contamination, resistance, metabolomics, and systemic remediation

“…The overall removal efficiencies of antibiotics can be calculated by the ratio of mass loads of influent and effluent [121]. The microorganisms are successful in degrading the antibiotics and reducing the environmental load/contamination, but the exact mechanism and pathways remain unclear [20]. However, the degradation can be accelerated using consortia.…”

Microbial degradation of four dispersed crude oils by Rhodococcus sp. evaluated using carbon stable isotope analysis

“…[30][31][32] CSIA was developed to evaluate biodegradation and quantify the progress of biodegradation of organic contaminants, including crude oil, 33 chlorinated ethenes, 29 BTEX, 32 pesticides 34 and sulfonamide antibiotics. 35 Normally, organic molecules with light carbon isotope are degraded faster, requiring less energy for bond cleavage at the reactive position, leading to 13 C enrichment in the residual substrates during biodegradation.…”